1. Field of the Invention
The present invention relates to a drive device using a polymer actuator formed of a polymer including an ionic liquid, and more particularly to a drive device capable of overcoming the tendency of the actuator to bow in a certain direction and preventing the ionic liquid from seeping out.
2. Description of the Related Art
As the structure of a polymer actuator of the related art, one having an electrolytic layer including an ionic liquid and a polymer, and electrode layers formed on two sides of the electrolytic layer is known. Application of a voltage across the electrode layers generates a stress difference between the surfaces of the two electrode layers due to migration and non-uniformity of distribution of ions in the polymer, resulting in the occurrence of bowing or deformation.
Japanese Unexamined Patent Application Publication Nos. 2009-77578 and 2009-5436 disclose methods of controlling a voltage applied to electrode layers of a polymer actuator.
In the method disclosed by Japanese Unexamined Patent Application Publication No. 2009-77578, a high-frequency inverted voltage is intermittently applied in a drive period in which a drive voltage is applied to the polymer actuator. Accordingly, unnecessary electrolysis of positive ions is suppressed, thereby improving the endurance.
In the method disclosed by Japanese Unexamined Patent Application Publication No. 2009-5436, a drive voltage is intermittently applied in a drive period in which the polymer actuator is driven, thereby suppressing a deformation backtrack phenomenon.
In a drive device for activating a driven member such as a protruding member with the use of bowing or deformation of the polymer actuator in a certain direction, the polymer actuator tends to deform in a protruding direction. On the surface that becomes convex upon bowing or deformation, the ionic liquid tends to be non-uniformly distributed and to seep out.
In both of Japanese Unexamined Patent Application Publication Nos. 2009-77578 and 2009-5436, the applied voltage is changed only in the drive period in which the polymer actuator is deformed. Even when such control of changing the applied voltage in the drive period is applied to the drive device for activating the driven member with the use of bowing or deformation in the certain direction, the tendency of the polymer actuator to deform in a driving direction may not be sufficiently overcome.